1. Field of The Invention
This invention relates to a ultrasonic motor and more particularly, to a friction member for use in ultrasonic motors.
2. Description of The Prior Art
This type of ultrasonic motor known in the art is, for example, a ultrasonic linear motor as shown in FIG. 1. The ultrasonic linear motor includes a pair of piezoelectric elements 1 driven with a driver D, a vibrator fixedly mounting the pair of piezoelectric elements 1 which is able to resonate with vibrations produced in the piezoelectric elements 1 and to amplify the vibrations, friction members 3, respectively, provided at opposite end portions of the vibrator 2, and a rail (a material to be driven) provided movably relative to the friction members 3.
The vibrations produced in the piezoelectric elements 1 are transmitted to the rail 4 through the vibrator 2 and the friction member 3. By this, a running body 10 (constituted of the piezoelectric elements 1, the vibrator 2 and the friction member 3 is moved relative to the rail 4 along the direction of the arrow (a)-(b).
In the above-described ultrasonic linear motor, the friction members 3 provided in sliding and relatively moving relation with the rail 4 should meet the following requirements.
The friction member or material should exhibit a good wear resistance on running of the ultrasonic motor, should not give any defects on the rail 4, should not suffer any defects on itself, and should not undergo any sticking on the rail 4 (a so-called sticking phenomenon).
The existing friction member 3 of the ultrasonic motor is mainly made of polyimide composite materials. However, such plastic materials have the drawbacks that when the temperature is elevated, the hardness of the materials is lowered, thus leading to more likelihood of sticking to the rail 4 with a greater abrasion wear.